Glycosidase Inhibitory Flavonoids from Sophora flavescens

The methanol extract of Sophora flavescens showed a potent glycosidase inhibitory activity. Active components were identified as well-known flavonoid antioxidants: kushenol A (1), (−)-kurarinone (2), sophoraflavanone G (3), 2′-methoxykurarinone (4), kurarinol (5), 8-prenylkaempferol (6), isoxanthohumol (7), kuraridin (8) and maackian (9). All flavonoids were effective inhibitors of α-glucosidase and β-amylase. Interestingly, lavandulylated flavanones 1—5 had strong α-glucosidase inhibitory activities, with IC50 values of 45 μM, 68 μM, 37 μM, 155 μM and 179 μM, respectively. Kushenol A (1) which does not bear a 4′-hydroxy group showed selective α-glucosidase inhibitory activity. Lavandulylated chalcone, kuraridine (8), exhibited IC50 value of 57 μM against β-glucosidase, which is the first report of a chalcone displaying glycosidase inhibition. Results showed that 8-lavandulyl group in B-ring was a key factor of the glycosidase inhibitory activities. The inhibition pattern was noncompetitive for α-glucosidase, whereas mixed inhibition was observed for β-amylase.